Loans and Allowance for Loan Losses - Summary of Changes in Related Party Loans (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Receivables [Abstract]
Balance, beginning of year	$ 5,565	$ 1,392
Advances	78	813
Repayments	(1,240)	(923)
Transactions due to changes in related parties		4,283
Balance, end of year	$ 4,403	$ 5,565